Reverse GST Calculator
Whenever a price or invoice already includes GST, the reverse GST calculation tells you how much of that amount is tax. This free reverse GST calculator opens in Remove-GST mode: enter the inclusive total, pick the rate, and instantly see the base amount before GST, the GST component, and the CGST + SGST (or IGST) split. Ideal for invoices, client bills, expense claims, input tax credit work and retail prices in India. Everything runs on your device — no sign-up, no uploads.
How to use Reverse GST Calculator
- 1
Enter the total including GST
Type the invoice or price amount that already includes tax.
- 2
Keep Remove GST mode selected
This page opens with the inclusive mode active, so GST is extracted from the total.
- 3
Pick the GST rate
Select the slab on the invoice: 5%, 12%, 18% or 28%.
- 4
Choose the sale type
Intra-state gives a CGST + SGST split; inter-state shows IGST.
- 5
Read base, GST and split
See the pre-GST amount, the GST component and the tax split immediately.
What reverse GST means
Forward GST adds tax to a net amount. Reverse GST does the opposite: when a total already includes tax, it works backwards to find the base amount and the tax hidden inside it. If you pay ₹11,800 for something that includes 18% GST, the base is ₹10,000 and the tax included is ₹1,800.
The reverse GST formula
Base amount = Total ÷ (1 + GST rate ÷ 100), and GST amount = Total − Base amount. At 18%, for example, the base is Total ÷ 1.18. The calculator applies this instantly and rounds the CGST/SGST split so the two halves always reconcile to the GST amount to the exact paisa.
Common GST rates in India
Indian GST slabs are 0%, 3%, 5%, 12%, 18% and 28%. Essentials like food grains sit at 0% or 5%, most processed goods and services around 12% and 18%, and luxury or demerit goods at 28%. Select the slab that applies to the item on your invoice — when no GST applies, use 0%.
Where reverse GST matters
Use it to validate inclusive prices on retail receipts, prepare reverse-charge entries, work out input tax credit from inclusive purchase bills, or reconstruct a net amount for quotations. You can also switch the sale type to break the tax into CGST + SGST for intra-state purchases or IGST for inter-state ones.
Private browser calculation
This is a pure browser calculation. Your amounts, rates and splits never leave your device — safe to use for business figures.
Examples
Invoice total includes 18% GST
- Input
- ₹11,800 inclusive at 18%
- Output
- Base ₹10,000 · GST ₹1,800 (CGST ₹900 + SGST ₹900)
Price includes 5% GST
- Input
- ₹1,050 inclusive at 5%
- Output
- Base ₹1,000 · GST ₹50 (CGST ₹25 + SGST ₹25)
Frequently asked questions
How do I remove GST from a total amount?
Divide the total by 1 + (rate ÷ 100). At 18%, divide by 1.18. This calculator does it instantly in Remove GST mode: enter the inclusive total, pick the rate, and read the base amount and the GST component.
What is the reverse GST formula?
Base amount = Total ÷ (1 + GST rate ÷ 100), and GST amount = Total − Base amount. Example: ₹11,800 ÷ 1.18 = ₹10,000 base, so the GST within the total is ₹1,800.
How do I calculate GST included in a price?
Use the reverse formula on the inclusive price: subtract the computed base amount from the total. The calculator shows both the base and the GST, plus the CGST + SGST (or IGST) split.
Which GST rate should I use?
Use the slab that applies to the goods or service on your invoice: 0%, 3%, 5%, 12%, 18% or 28%. Most business-to-business items fall at 18%; essentials at 5% or 0%. When in doubt, your invoice should state the rate.
Is this calculator India-specific?
Yes. It uses Indian GST slabs and splits the tax into CGST + SGST for intra-state supplies and IGST for inter-state supplies, exactly as Indian invoices are drawn.
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Last updated 12 August 2026